Abstract: A DC motor driven power steering system for a motor vehicle includes a motor current detection circuit for detecting a motor current flowing through the DC motor, a power supply voltage detection circuit for detecting a power supply voltage applied to the bridge commutation circuit, a motor voltage estimating unit for estimating a voltage applied across the DC motor on the basis of the power supply voltage applied to the bridge commutation circuit and the pulse-width modulated control signals used for controlling the bridge commutation circuit, and a motor rotation detecting means for detecting the rotation state of the DC motor on the basis of the motor current and the estimated motor voltage applied to the DC motor. High reliability can be ensured for detection of the rotation state of the DC motor.

Abstract: An interface apparatus for fan monitoring and control includes a current source amplifier that generates a programmable current in response to its input voltages. Associated with an output capacitor, which is able to reduce noise, the programmable current drives the fan at a desired speed. The rotating fan induces a ripple signal in the output capacitor, which is fed to a band-pass amplifier to produce a tachometer pulse. Through a buffer amplifier, an input control signal combined with a thermal sensor signal has direct control over the current source amplifier. Alternatively, a PWM circuit having a comparator, a ramp oscillator and the output of the buffer amplifier drives the current source amplifier in switching mode. Since the ramp oscillator can be synchronized by the input, both analog and pulse signals can function as the input control signals.

Abstract: A motor driver circuit for a three-phase wound disk drive spindle motor having multiple phase coils and corresponding coil drivers, and commutation phase generation means responsive to BEMF voltage zero crossings of the phase coils for generating commutation cycle control signals for the motor phases.

Abstract: A high voltage, single-stage variable speed motor power supply utilizes direct AC-to-AC converters that do not have any intermediate DC link, along with a multi-level, multi-phase, multi-circuit variable speed motor drive and a motor in which a stator is wound with a number of multi-phase circuits. Each multi-phase circuit includes semiconductor switches arranged in drive switch pairs which are operated to produce an effective DC supply with the switches being controlled so that the most positive line-to-line source voltage is utilized for the inversion process.

Abstract: A speed control system for a brushless repulsion motor of the type including a series of armature mounted switches for shorting circumferentially spaced armature coils, said system comprising: a digital counter on the armature for creating a repetitive succession of switch activating signals in a selected sequence at a given rate determined by the counting rate of the counter; means for activating the switches with the signals in the sequence and at the rate to control the speed of the armature; and, means for directing a reference pulse signal at a reference frequency to the counter to set the counting rate of the counter.

Abstract: The invention relates to a method for adjusting a real value (actual value) of a physical quantity to a preset value (target value) with the following steps:(a) the difference between the target value and the actual value (referred to below as the control deviation) and its sign (referred to below as the control sign) is determined repeatedly at interval; (b) the control deviation is converted into at least one electrical signal during or after each measurement, and the duration thereof (referred to below as the control deviation duration) is proportional to the absolute value of the control deviation at least in the range of the target value, and the value thereof is a function of the control sign; (c) the charge of an analog electrical memory arrangement is affected by this at least one electrical signal during the control deviation duration; (d) depending on the value of the charge of the memory arrangement, the physical quantity is directly or indirectly affected to keep it in the range of the target valu

Abstract: A motor drive apparatus and an air-conditioner using the motor control apparatus has a feature which allows it to gradually increase a dc voltage value to a predetermined value when starting the switching operation of a chopper circuit by dc voltage control thereof, and when stopping the switching operation of the chopper circuit to be able to gradually decrease the dc voltage value to a predetermined value. Further, the dc voltage command value is adjusted so as to make it possible to maintain a preferred value of dc voltage. Thereby, fluctuation in the number of revolutions of the motor can be prevented even if the converter is started or stopped while the motor is operating, thereby allowing the motor drive apparatus and air-conditioner using the motor control apparatus of the invention to be operated at their maximum capacities.

Abstract: A display system using red, green, blue, and white light. The system derives data for the white portion of a color wheel or a white device from the red, green and blue data. The white portion of the color wheel is controlled as if it were another primary color on the wheel. Errors are prevented by a correction applied if the unfiltered light from the source has a different color temperature than the white light produced using the red, green and blue segments of the color wheel, or the devices for those colors. Analysis is performed on the data to determine if white light is necessary to be added to each frame of data.

Abstract: A pump motor control apparatus is adapted to control a pump motor of a forklift truck by using a driving transistor connected between a battery and the pump motor. The pump motor control apparatus includes a current detection circuit for detecting a current flowing through the pump motor to generate a current detection signal representing the current. A controller is employed to determine the load condition based on the current detection signal to thereby generate a control signal for use in the control of the driving transistor. The control signal is a pulse width modulation signal whose on-duty ratio is controlled depending on the load condition so as to decrease the torque and speed of the pump motor during the unloaded condition but to increase the torque and speed of the pump motor during the loaded condition.

Abstract: In a multiple print head printer in which print heads are removable and exchangeable, a method of controlling a printer carriage motor comprises the steps of receiving a print job, the print job comprising print commands and print data, determining a type of print mode to print the print data based on the received print commands, detecting a number of print heads installed in the multiple print head printer, selecting a motor control function for controlling operational speed and direction of the printer carriage motor based on the determined type of print mode and the detected number of print heads.

Abstract: A method and apparatus for determining the critical dwell time required between firing pulses generated by a PWM inverter to eliminate greater than twice overvoltage on motor supply lines. Critical dwell time is correlated with line parameters including inductance and resistance per unit length and is then provided to a controller to alter voltages provided to a motor to eliminate overvoltage.

Abstract: An apparatus for controlling an electric assist steering system (10) having an electric assist motor (26) operatively connected to a steerable member. Energization of the motor provides steering assist to the steering member. The apparatus includes a steering torque sensor (27) for sensing applied steering torque and providing a torque signal indicative thereof. A first switching device (72) is operative coupled between one terminal of the electric assist motor (26) and a first terminal of a source of electrical energy. A second switching device (98) is operative coupled between a second terminal of the electric assist motor and a second terminal of the source of electrical energy. A controller (76) periodically switches the first and second switching devices between ON and OFF conditions so that the ON condition of each the first and second switching devices is less than one-hundred percent of a period and a portion of the ON condition of the first and second switching devices overlap.

Abstract: An apparatus for controlling the speed of rotation of the rotor of a brushless DC motor wherein means are provided for shifting both the on and off angle of motor excitation in opposite senses to thereby widen or narrow the pulse of energization to motor winding(s).

Abstract: A motor control method and apparatus for spindle motor control and for voice coil motor (VCM) control in a direct access storage device (DASD). Characteristics of the pulse width modulation (PWM) waveform are adapted to allow tradeoffs to be made between lower noise emission, greater power efficiency, and current ripple in the motor in order to optimize the driver operation. The transition rate of the PWM waveform is modified by changing the "off-time", which is maintained as a constant in a control register, in response to a change in the condition or mode of operation of the DASD. The "slew rate" of the PWM waveform is also controlled by a changing the value of a constant stored within the control register and can be modified in response to changes in the condition or operational mode of the DASD.

Abstract: A hybrid DC motor controller is provided for driving a DC motor. A switch is connected in series with the DC motor, and a capacitor is coupled in parallel with the DC motor and the switch. The speed of the DC motor is controlled by the capacitor voltage and the duty cycle of a pulse-width modulated (PWM) signal supplied to the switch. The hybrid controller combines a motor speed control loop with a PWM optimization loop. The motor speed control loop generates a PWM signal in response to the speed of the DC motor and conducts that PWM signal to the switch to control the DC motor. The PWM optimization loop includes a controller that is responsive to the PWM signal and an AC voltage signal. This controller compares the PWM signal with a PWM signal setpoint, and drives the PWM signal toward the PWM signal setpoint by adjusting the capacitor voltage in response to the comparison between the PWM signal and the PWM signal setpoint.

Abstract: A method and apparatus for adjusting torque in an electric impact torque wrench. A current sensing circuit passes current through a power relay for powering an electric impact torque wrench. The power relay is normally in a conducting state. The current sensing circuit includes a threshold current indicator which is activated when current flowing through the current sensing circuit reaches a predetermined threshold amount. The threshold current indicator is provided to a first timer which counts an activation-off time since the threshold indicator is activated, the first timer presuming that the current has remained above the predetermined threshold amount during this time. At the conclusion of the activation-off time, the first timer signals a time-off extender circuit.

Abstract: The speed of a rotor in a two-winding, permanent magnet motor can be accurately controlled with a dual-polarity pulse width modulation drive signal. The phase back emf signal generated in the non-excited winding is compared against the phase of a command signal and the results of the comparison are used to vary the duty cycle of the drive signal.

Abstract: The circuit for speed regulation of a three-phase motor incorporates a drive connected directly to a three-phase mains (R,S,T) which allows through mains voltage directly to the motor windings controlled by a pulse-width modulated signal produced by a control circuit controlled by the motor speed and fed to the drive stage via circuits for galvanic (d.c.) separation of the control circuit and the drive stage. The galvanic separation is produced with solar cell components.

Abstract: A distributed power supply for a motor controller including electronic control circuits for controlling IGBT power transistor stages. The power supplies for the power transistors and gate drivers therefor are isolated from the power supplies for the electronic control circuits. Each of the gate drivers for the IGBT power transistor is supplied through a separate floating supply. Power supplies for the digital components and the analog components have separate ground return paths and are tied together at the supplies.

Abstract: The invention is concerned with an electronic control unit (1) for the electric motor of a vacuum pump (100) comprising a suction port (119), an exhaust port (120) and pumping stages formed by rotor disks (113, 114) secured to a rotating shaft driven by an electric motor, and stator rings (115, 116) secured to a pump housing (101) and cooperating with said rotor disks. The unit (1) comprises: a housing (2), first leads (50) for electrically feeding the control unit, second leads (60) for electrically feeding the motor of the pump (100), a circuit for generating a voltage adapted to feed the motor, the circuit generating drive signals (A, B, D, E, G, H, PWM) and providing at least a pulsating signal (PWM the width of which for combining said drive signals can be modulated, and means (201, 202, 203) for combining the, pulsating signal (PWM) with at least one of the drive signals (A, D, G) so as to change the rms voltage of said voltage system.

Abstract: An electric motor (12) is supplied with current (i.sub.mot) via a semiconductor switch (14). During operation, the semiconductor switch (14) is driven by a Pulse Width Modulation (PWM) unit 15 using a pulse-formed signal (32). For regulation of the duty ratio of this pulse-formed signal, a first analog signal, which is a function of at least a first motor parameter, is fed to the PWM unit. Further, a second analog signal (STBGR), which is a function of at least a second motor parameter, is fed to the PWM unit for regulation of the duty ratio. As long as the second motor parameter does not exceed a predetermined value, the duty ratio is predominantly controlled by the value of the first analog signal. When the second motor parameter exceeds the predetermined value, the duty ratio is at least predominantly controlled by the value of the second motor parameter, in order to control this second motor parameter through the PWM unit.

Abstract: A PWM speed regulating apparatus for DC elevator comprises a rectifier-filter (1), voltage suppressor (2), chopper voltage regulator (3), system controller (4) and a driving protector (5). The speed of DC motor is regulated by a pulse width modulating mode so that the current of the motor is maintained continuously and the ripple of current and torque is lower, and which ensures a good riding quality and a high floor arrival accuracy.

Abstract: A controller controls the running speed of a variable speed motor of the type which runs at a speed related to the duty cycle of a pulse width modulated drive voltage applied to it and to the load being applied. The controller includes a setting switch for setting the motor running speed and a device for measuring the load being applied to the motor. Also included is a data storage for storing data representing a plurality of different pulse width modulation duty cycles for driving the motor at various desired motor running speeds and with various loads being applied to the motor. A processor is operatively connected to the setting switch, the load measuring device and the data storage for generating signals representing a particular duty cycle corresponding to a desired running speed setting and applied load to result in the desired motor speed. The processor generates these signals at a predetermined time interval to reach and maintain the desired motor speed.

Abstract: The method for controlling a motor driving a load holds the speed of the output shaft of the motor substantially constant as the torque imposed upon the shaft by the load varies, then regulates the rate of change of the output torque delivered by the motor's output shaft as the motor's speed decreases.

Abstract: A motor driving apparatus PWM-controls a DC voltage from a rectifying unit according to a rotation speed setting information, and drives a motor by voltage pulse chooped by PWM. The rectifying unit is controlled so that a full-wave rectification is performed when the motor runs at a rotation speed below a prescribed rotation speed and a voltage-doubler rectification is performed when the motor runs at a rotation speed above the prescribed rotation speed. On the other hand, in case a motor drives a compressor of an air-conditioning system, the rectifying unit is controlled so that the full-wave rectification is performed when the air-conditioning system is a cooling operation and the voltage-doubler rectification is performed when the air-conditioning system is a heating operation.

Abstract: In order to prevent the performance of a motor from deteriorating due to a change in which the rotation rate of its rotor is to be increased suddenly, in a brushless motor in which a drive pulse whose pulse width is modulated in correspondence to a rotation rate setting signal input from the outside is formed and switching control is performed on the current supplied to the exciting coils by using output signals from the Hall elements that detect the position of the rotor and the drive pulse, the pulse width of the drive pulse is changed gradually and greatly until it reaches the pulse width that corresponds to the rotation rate setting signal when the upward change in the rotation rate of the rotor is to be large.

Abstract: A dc motor speed control circuit is provided. A first circuit utilizing an opto-electric sensor for providing an input signal corresponding to a desired dc motor speed is connected to a second circuit and the second circuit is connected to the dc motor, wherein the second circuit responds to the input signal and causes current to flow through the dc motor corresponding to the input signal. A temperature circuit, voltage level circuit and current level circuit may also be connected to the second circuit to control the dc motor.

Abstract: An apparatus for controlling a stepping motor used for moving a carriage having a pickup from a first position to a second position, the apparatus having: a calculating device for calculating a moving distance between the first position and the second position; a setting device for setting an acceleration area to accelerate the stepping motor and a deceleration area to decelerate the stepping motor, on the basis of the moving distance; and a driving device for driving the stepping motor by a one-two-phase excitation method until rotation velocity of the stepping motor increases to a predetermined velocity in the acceleration area, driving the stepping motor by a two-phase excitation method after rotation velocity of the stepping motor increases to the predetermined velocity in the acceleration area, driving the stepping motor by the two-phase excitation method until rotation velocity of the stepping motor decreases to the predetermined velocity in the deceleration area, and driving the stepping motor by the o

Abstract: A power amplifier (18) for driving a brushless DC motor (22) includes a processor (40) which receives a signal indicative of motor situational usage and generates a mode state signal indicative of which one of a plurality of amplification modes is to be implemented in response to the received signal. The amplification modes include a linear mode and a switching mode, with the switching mode including a two quadrant switching mode and a four quadrant switching mode. The amplifier (18) further includes a controller (50) which, in response to the mode state signal, generates control signals for each of coil drive circuits (26) associated with the motor. Further, in response to a signal indicative of motor situational usage, processor (40) generates a power state signal which causes controller (50) to connect coil drive circuits (26) to a suitable one of a plurality of differing voltage sources (21, 23).

Abstract: The invention relates to a method for driving an electric motor (1) which is employed, in particular, in manually guided electric tools, such as drilling machines, screwing machines or the like. Variable pulses of an electric voltage are applied to the electric motor (1) in such a way that the rotor of the electric motor (1) moves at a rotational speed which can be set. In order that the rotor of the electric motor (1) moves intermittently or abruptly, at least parts of at least individual pulses are blanked by superposition of a pulse interval having a zero voltage. A circuit arrangement for a method of this type has control electronics (5) and an electronic power switch (4), such as a triac, a transistor, an IGBT or the like, which is switched by the control electronics (5) in such a way that the variable pulses can be applied to the electric motor (1) via the electronic power switch (4).

Abstract: Masking of switching noise is implemented in the driving system of an "H" bridge stage by exploiting the periodic signal generated by a PWM control circuit (normally present in the control system for controlling the "H" bridge in an open-loop mode) for masking the decay time of the disturbances caused by the switching from off-to-on of a first pair of switches of the bridge that drive a current in a certain direction through the load. This is implemented by keeping high for a preset period of time the periodic signal generated by the PWM circuit and varying the duty-cycle of the signal for regulating the mask time in function of the load characteristics.

Abstract: A motor driving apparatus enabling direct pulse width modulation driving (direct PWM driving) in a sensor-less motor. The motor driving apparatus includes a comparison unit for comparing back-electromotive voltages appearing in respective phases of a multi-motor, a pulse width modulating unit for outputting pulse width modulated signals for rotationally driving the motor based upon a rotational error signal of the motor, a minimum pulse width detection unit for detecting the minimum pulse width position of the pulse width modulated signal from the pulse width modulation means, a sample-holding unit for sample-holding comparison outputs of the comparison means at a timing of detection of the minimum pulse width of the pulse width modulated signal from the minimum pulse width detection unit, and a motor driving unit for rotationally driving the motor based upon each sample-and-hold output from the sample-and hold unit.

Abstract: Weaving apparatus comprises a warp beam bearing warp threads, a loom on which the warp threads are woven with weft threads, and a take-up roller for taking up the woven material. The loom is powered by a main loom motor. Either or both of the take-up roller and the warp beam are controlled by switched reluctance motors. The switched reluctance motor is able to maintain correct tension in the warp threads or the woven material without generating excessive heat in maintaining a desired position.

Abstract: An apparatus for driving an electric motor, including a full-wave rectifier which rectifies an alternating current supplied from an alternating-current power supply, and supplies a full-wave rectified current to the motor, a chopper which chops the full-wave rectified current supplied from the rectifier to the motor so that the chopped current is applied to the motor, and a control device which generates a chopping pulse signal having a first signal characteristic corresponding to a given motor control target and a second signal characteristic to reduce an alternating-current component of the full-wave rectified current supplied to the motor, the control device supplying the chopping pulse signal to the chopper so that the chopper chops the full-wave rectified current according to the chopping pulse signal.

Abstract: A minimum fan RPM control circuit constantly turns a computer exhaust fan at a minimum RPM while the computer is on. The RPM control circuit includes a blanking and reset circuit responsive to a ramp signal, for generating a reset pulse at a reset output. The RPM control circuit also includes a latch circuit conductively coupled to the reset output, the latch circuit responsive to the reset pulse, and responsive to a tachometer pulse, for generating a latch pulse at a latch circuit output. The RPM control circuit further includes an integration node conductively coupled to the latch circuit output, and responsive to the latch pulse, for generating an integral signal of the latch pulse. Finally, the RPM control circuit includes a power switch driver conductively coupled to the integration node, and responsive to the ramp signal and the integral signal, for generating an RPM control pulse.

Abstract: A method and apparatus for controlling the speed of a multi-phase, brushless DC electrically commutated motor (ECM). Voltage is commutated to the windings of the ECM based on rotor position information derived from back EMF or Hall effect sensors. The application of the commutating voltages is arranged such that the voltage applied to the windings always leads the back EMF generated in the windings by a selected constant lead angle. The speed of the motor is then controlled by pulse width modulating (PWM) the voltage applied to the windings of the ECM.

Abstract: A system and method is disclosed for feedback velocity control of a D.C. motor. The system includes a motor (30) which is represented by its circuit equivalent--a series combination of an inductance (32), a resistor (34) and a back EMF source (36). The drive to the motor (30), supplied by a controller, is periodically inhibited by timing logic (22) and AND gate (20). Once the inductive transient decays via clamping diode (38) such that the motor current is zero, switch (40) is closed and the internally generated motor voltage is sampled by a capacitor (42). A/D converter (44) transforms the sampled value to a digital value and sends it to the controller. The controller compares it to a predetermined desired value then makes the necessary adjustments to the drive signal.

Abstract: A control apparatus for an electric power steering system assures stability of the feedback control and control generation of noise from the control circuit when the steering wheel automatically returns to the neutral position by means of the self-aligning torque in order to improve the feeling of the steering operation. In the motor driving circuit connecting four semiconductor elements in the shape of H bridge, the semiconductors of the first arm are driven by the duty ratio D1 while the semiconductors of the second arm are driven by the duty radio D2 defined by the function of the duty ratio D1 (D2 is longer in time than D1).

Abstract: A method for triggering or controlling a final control element uses a pulse width modulated signal. A sequence of the pulse width modulated signal is fixed by a predetermined time raster. After a predetermined number of standard pulses, one standard pulse is emitted and one long pulse follows that is twice as long as one standard pulse. In this way, seizing of the final control element is reliably prevented.

Abstract: A brushless DC motor system using PWM switching, in which the PWM switching is temporarily frozen whenever a zero crossing is expected in the back EMF. This avoids disruption of zero-crossing detection due to switching transients from the power transistor.

Abstract: A power steering motor control unit for driving a motor in a PWM mode with feedback motor current control reduces fluctuations in the output torque of the motor caused by switching among a plurality of motor driving modes or a change in the duty value of the PWM signal. The control unit as a switching device driving circuit for driving the motor in the PWM mode and a plurality of motor driving modes for the driving control system of a motor, Q/D switching circuitry 14 for switching the motor driving mode, and detected current correcting circuitry 16 for correcting at least one input signal of an input signal comparing circuit provided in a feedback control loop in accordance with the motor driving mode. When the motor driving mode is switched, the correction value given by the detected current correcting circuitry is changed.

Abstract: A PWM controlled multiphase DC motor apparatus has a multiphase DC motor, a current sensor, and a PWM controller. The DC motor has multiple windings which turn on and off during commutation at a commutation frequency. The current sensor is coupled to sense power supply current flowing in all windings of the DC motor. The PWM controller is coupled to control the DC motor using a PWM signal at selected PWM frequency with variable duty cycle. Using the feedback from the current sensor, the PWM controller maintains approximately constant torque in the DC motor by adjusting the duty cycle of the PWM signal. The PWM controller includes a soft switching circuit which manipulates a voltage used to generate the controlling PWM signal in a manner which causes linear stewing of currents in the windings during commutation. The linear current stewing occurs at a slew rate that is slow relative to the PWM frequency to thereby reduce torque ripple during commutation.

Abstract: A digital motor control is described which is programmable and has dual digital phase with sliding proportionality such that the motor control adaptively alters a speed of a motor by both changing sign and altering motor speed proportionally to an amount of motor speed error.

Abstract: A pulse width modulated (PWM) motor drive with back EMF monitoring of the floating phase of a polyphase motor is arranged so that zero crossings of the back EMF can be read without interference by PWM switching. A measure is taken of an interval between two zero crossings and, in the next interval, the PWM switching is stopped near to and before the next expected zero crossing, based on the time of the last prior interval. A period counter counts up during the first interval and another counter, loaded with the previous count reached by the period counter, counts down at the same rate during the second interval until a certain number is reached, near to but before zero, to generate a signal that results in stopping PWM switching until after the next zero crossing is detected.

Abstract: A disk drive has a microprocessor, a digital controller chip, and an analog power chip, and a multi-winding spindle motor. The power chip operates under gross and fine control to connect and disconnect, during ON and OFF phases, a supply voltage to each winding on a PWM basis. The magnitude of the supply voltage and the temperature of the power chip vary. The microprocessor sends a digital control signal to the controller chip for gross control. The controller chip sends a PWM signal to the power chip for fine control. The power chip has pins for receiving the supply voltage, for sending a modulated signal to the controller chip; and for receiving the PWM signal from the controller chip.

Abstract: A distributed power supply for a motor controller including electronic control circuits for controlling IGBT power transistor stages. The power supplies for the power transistors and gate drivers therefor are isolated from the power supplies for the electronic control circuits. Each of the gate drivers for the IGBT power transistor is supplied through a separate floating supply. Power supplies for the digital components and the analog components have separate ground return paths and are tied together at the supplies.

Abstract: An FET switch and an inductor in series with a DC motor supply voltage pulses at a high frequency, a power diode permits current recirculation, and a capacitor connected to the motor maintains a mean DC voltage level on the motor which is proportional to the switching duty cycle. The motor speed is proportional to the mean voltage. Smoothing due to the capacitor and the inductor converts the voltage pulses due to switching to a small sinusoidal ripple to attain low radiated emissions.

Abstract: A noise dithering system provides gating signals to switching transistors that selectively apply power to an output device in response to the gating signals, wherein said gating signals include a selected level of frequency modulation insufficient to alter operational characteristics of the output device more than a predetermined amount. One embodiment concerns a PWM switching system in which a PWM controller provides gating signals to switching transistors, where the gating signals are clocked by a timing circuit in accordance with a modulated input reactance sensed by a timing input node. In another embodiment, the gating signals may be clocked by the timing circuit in accordance with a modulated current at a timing input node, provided by a variable current source. In the case of the modulated input reactance, a voltage variable capacitor is preferably used to provide a capacitance proportional to output of a modulator.

Abstract: An electrically-operated steering apparatus in which in addition to avoiding an increase in cost caused by installing a new sensor or using a high process speed CPU, steering feels, such as steering wheel return, viscous feeling, inertial feeling and frictional feeling, are improved. In addition to assisting a static steering torque on the basis of a torque sensor, with a motor-applied voltage detection circuit capable of removing the square wave component attendant on the PWM drive of a motor, a motor angular velocity .omega. is estimated from the output data of the relevant circuit. A motor angular acceleration d.omega./dt is estimated from the motor angular velocity .omega. by using a differential calculator. The steering friction and the moment of inertia are compensated on the basis of the motor angular velocity .omega. and motor angular acceleration d.omega./dt, respectively.

Abstract: A power tool such as an electric drill typically contains a gear train that couples the output spindle of the motor to the tool bit-receiving chuck and has associated therewith a degree of looseness which must be taken up before torque from the motor is applied to the tool bit. The control circuit for the power tool increases the effective torque output of the tool after a predetermined torque level is attained, by alternately turning the motor on and off, with the duration of the off-time sufficient to permit the gear train to relax, thus giving the motor a "running start" when power is reapplied. Various alternative schemes for transitioning to this ratcheting mode of operation are disclosed including the sensing of a predetermined threshold current, a predetermined increase in motor current, and a predetermined rate of deceleration in motor speed.